that looks like Staphylococcus aureus. i used to get staph from wearing rubber gloves when working with shellfish, but ive never seen it so bad.
the bacteria are everywhere, but the infection seems to show up when your hands are wet or sweaty for extended periods, i think because the bacteria are building up in sweat glands. antibiotics will do little good IME, try using antibacterial hand wash and either surgical spirit or isopropyl alcohol (IPA).
surgical spirit/rubbing alcohol will dry your skin out which may lead to cracking and secondary infection, but IPA seems to be available everywhere nowadays as a hand wash and is not so harsh

I'm not a doctor.... But it sure as he'll doesn't look like eczema to me.

Apart from speed of growth, is everything else the same as you had on your thumb?
If so
Is it same hand as when it was on your thumb.
If so
Was the weather/environmental conditions the same when you had it on the thumb?

What do you do for a job? Are you handling solvents? Are you having to wash your hands a lot?

The one on my thumb was on the same hand. In both cases it started with a tiny scratch.

Last time I tore the blister open during randori (at the training camp following judo senior nationals, before I realized that the blister was growing), so the blister remained dry as it grew. This time the skin has remained intact because it started growing on Friday evening after I got off work. Therefore, the blister has remain moist on the inside. Maybe that's why it's growing faster?

At work, I don't handle chemicals of any kind. I work with communications equipment. I believe I got the scratch while at work on Friday. I was handling cable that was a bit dusty from being dragged on the floor in an office. So I guess it could be common floor bacteria (which includes staph and strep, of course) or a bacteria that has already colonized my skin (I've grappled for many years, so that probably includes everything that can possibly colonize a human's skin). I don't wash my hands more or less than average.

I read on the web that steroid cream can make a bacterial or fungal infection worse. I hope that the doctor is right about this not being a bacterial infection.

Go see a dermatologist, NOT a general doctor. Most general doctors don't know the first fucking thing about dermatological conditions, which ALL look the same. It could be staph, MSRA (also staph) or a million other things, it could be your body's immune system, or it could be a subcutaneous mycoses (ie fungal infection under the skin).

If the lymph (the liquid in the blister) is CLEAR or CLEAR YELLOW, it's likely an autoimmune thing (ezcema). If it's opaque, unclear yellow, or cloudy it's definitely infected.

You'll know once you start using the steroid ointment because if it's autoimmune, the steroids will have a noticeable effect.

Note that the current recommendation from the entire dermatological community is to SOAK your hand in cool water for 20 minutes THEN smear the medicine and leave it on. Don't use soap or hot water on it. This is called the "soak and smear" method and it is 1000x more effective than just putting on the medicine. The soaking makes the medicine work much more efficiently and removes unwanted types of skin cells.

That all said, if the steroids don't make this go away within days, you need to see a DERMATOLOGIST.

I have serious autoimmune issues from childhood and soak and smear has become a staple of my adulthood. The worst thing you can do is go to general practicioners who (I know from experience) will look at this over and over and keep telling you "it's not infected, here use this cream" and you'll suffer for years until you get proper medical advice.

I had MRSA last year. What you have (in the first pic) looks like regular wart. I have no idea about the growth rate of warts though, as I've never had one. Although I believe I read earlier that staph/MRSA can take different forms. I really don't know. I can only comment on my experience with MRSA.

Pretty damned painful first off, mainly in the surrounding area of the bump/wound. Surprisingly in my case the actual wound didn't hurt that bad. Could keep you out of work for a few weeks as it is ridiculously contagious. Has to heal from the inside out as it eventually will become an open wound (a hole in you body wherever it is located, in my calf in this case), and will leave a nasty scar.

In my case, although I frequent jails (professionally), locker rooms, and gyms both paid for and free provided by the P.D., I honestly think mine was the result of a bug bite. I distinctly remember checking an alarm at an abandoned house, finishing up, sitting in my car out front, and then scratching my calf as the result of what I thought was getting bit by something. No biggie right? Until over the course of a week it developed into what looked like a white head. Therefore I fucked with it. It didn't go away. Got bigger, redder, and more hot to the touch.

After a week I went to the doc. He said staph, tested for staph/MRSA, and then began MRSA antibiotics even before the lab results came back. It was MRSA.

Point is... Go to the doc, or another doc for a 2nd opinion, or possibly risk losing a limb, or death do to blood poisoning. Tell your instructors, and don't go near your gym till you get the ok from said doc. Written ok will prob ease your instructor's worries a bit. Oh yeah, use you own **** in training ie- gloves, pads, head gear.

PS - finally a post I can comment on without being reamed for necro-posting. Or whatever you folks call it.

You'll know once you start using the steroid ointment because if it's autoimmune, the steroids will have a noticeable effect.

Steroids can also have a noticeable effect on non-autoimmune conditions, though, since even if it’s fungal or bacterial, steroids still have an anti-inflammatory effect and reduce itching and swelling. The difference is that if it’s autoimmune, the immunosuppressant effect of the steroids actually fix the problem, whereas if it’s something else, they just suppress some of the symptoms while leaving the infection to thrive. Ringworm in particular seems to thrive on steroid cream, spreading gleefully even as you think you’re getting better because some of the symptoms temporarily abate.

I know this from personal experience of having ringworm misdiagnosed, being prescribed a steroid cream, and having it spread as a result.